Implement passing configuration over environment variables

README.md

@@ -56,6 +56,15 @@ Installation
 
 For example, if your python path includes '/path/to/myproject' and you include `plugins.repeat.RepeatPlugin` in ACTIVE_PLUGINS, it will find the RepeatPlugin class within /path/to/myproject/plugins/repeat.py and instantiate it, then attach it to your running RTMBot.
 
+### Environment variables
+
+All of the configurations variables mentioned can be overriden using environment
+variables. For example, the following will override slack token.
+
+    $ SLACK_TOKEN="xoxb-foo-bar" rtmbot
+
+This is especially useful when you want or need to hide credentials.
+
 A Word on Structure
 -------
 To give you a quick sense of how this library is structured, there is a RtmBot class which does the setup and handles input and outputs of messages. It will also search for and register Plugins within the specified directory(ies). These Plugins handle different message types with various methods and can also register periodic Jobs which will be executed by the Plugins.
@@ -127,6 +136,29 @@ The repeat plugin will now be loaded by the bot on startup. Run `rtmbot` from co
     rtmbot
 ```
 
+###  Configuration
+
+You can configure your plugins using `rtmbot.conf` and environment variables.
+For example, running the following
+
+    $ REPEAT_PLUGIN_DUMMY_VARIABLE="true" rtmbot
+
+will result in effectively same as the following `rtmbot.conf`:
+
+```
+        plugins.repeat.RepeatPlugin:
+            dummy_variable: "true"
+```
+
+Note that environment variable values are treated as strings. If you need to
+override for example lists, booleans or numbers, handle it in your plugin. Plugin
+configuration can be accessed in the plugin from `self.plugin_config`.
+
+```python
+    def process_message(self, data):
+        print(self.plugin_config['dummy_variable']) # prints "true"
+```
+
 Create Plugins
 --------
 

rtmbot/bin/run_rtmbot.py

@@ -3,6 +3,7 @@
 import sys
 import os
 import yaml
+import re
 
 from rtmbot import RtmBot
 
@@ -20,12 +21,61 @@ def parse_args():
     return parser.parse_args()
 
 
+def prefix_from_plugin_name(name):
+    basename = name.split('.')[-1]
+    # Attribution: https://stackoverflow.com/a/1176023
+    splitted = re.sub('(.)([A-Z][a-z]+)', r'\1_\2', basename)
+    return re.sub('([a-z0-9])([A-Z])', r'\1_\2', splitted).upper() + '_'
+
+
+def load_overrides_from_env(config):
+    '''
+    Read and apply overrides from environment variables. For plugins, name of the class
+    is turned into a prefix. For example:
+        YourAwesomePlugin.foo_bar => YOUR_AWESOME_PLUGIN_FOO_BAR
+    '''
+    def boolish(v):
+        return v == '1' or v == 'true'  # bool('false') == True, so do it the hard way
+
+    params = [
+        {'name': 'SLACK_TOKEN', 'type': str},
+        {'name': 'BASE_PATH', 'type': str},
+        {'name': 'LOGFILE', 'type': str},
+        {'name': 'DEBUG', 'type': boolish},
+        {'name': 'DAEMON', 'type': boolish}
+    ]
+
+    # Override the rtmbot-specific variables. Here we can take advantage
+    # of the fact that we know what type they are supposed to be in.
+    config.update({
+        param['name']: param['type'](os.environ[param['name']])
+        for param in params
+        if param['name'] in os.environ})
+
+    # Override plugin-specific variables. Since we don't know a schema,
+    # treat values as string. Leave type conversion for plugins themselves.
+    for plugin in config.get('ACTIVE_PLUGINS', []):
+        prefix = prefix_from_plugin_name(plugin)
+        plugin_configs = [
+            var for var in os.environ
+            if var.startswith(prefix)]
+
+        # Create if necessary
+        if plugin not in config:
+            config[plugin] = {}
+
+        config[plugin].update({
+            param.split(prefix)[-1].lower(): os.environ[param]
+            for param in plugin_configs})
+
+
 def main(args=None):
     # load args with config path if not specified
     if not args:
         args = parse_args()
 
     config = yaml.load(open(args.config or 'rtmbot.conf', 'r'))
+    load_overrides_from_env(config)
     bot = RtmBot(config)
     try:
         bot.start()

tests/test_rtmbot_runner.py

@@ -0,0 +1,79 @@
+import os
+
+from contextlib import contextmanager
+from rtmbot.bin.run_rtmbot import load_overrides_from_env
+
+@contextmanager
+def override_env(env):
+    _environ = dict(os.environ)
+    try:
+        os.environ.clear()
+        os.environ.update(env)
+        yield
+    finally:
+        os.environ.clear()
+        os.environ.update(_environ)
+
+def test_normal_overrides():
+    config = {
+        'SLACK_TOKEN': 'xoxb-foo-bar',
+        'BASE_PATH': os.getcwd(),
+        'LOGFILE': 'foobar.log',
+        'DEBUG': True,
+        'DAEMON': True
+    }
+
+    override = {
+        'SLACK_TOKEN': 'xoxb-this-should-change',
+        'BASE_PATH': '/opt/nope',
+        'LOGFILE': 'awesome.log',
+        'DEBUG': 'false',
+        'DAEMON': 'false'
+    }
+
+    with override_env(override):
+        load_overrides_from_env(config)
+        expected = {
+            'SLACK_TOKEN': 'xoxb-this-should-change',
+            'BASE_PATH': '/opt/nope',
+            'LOGFILE': 'awesome.log',
+            'DEBUG': False,
+            'DAEMON': False
+        }
+        assert config == expected
+
+def test_plugin_overrides():
+    config = {
+        'ACTIVE_PLUGINS': ['plugins.AwesomePlugin']}
+
+    override = {
+        'AWESOME_PLUGIN_FOO': '1',
+        'AWESOME_PLUGIN_BAR_BAR': 'some_awesome_value'
+    }
+
+    with override_env(override):
+        load_overrides_from_env(config)
+        expected = {
+            'foo': '1',
+            'bar_bar': 'some_awesome_value'
+        }
+        assert config['plugins.AwesomePlugin'] == expected
+
+def test_plugin_config_already_exists():
+    config = {
+        'ACTIVE_PLUGINS': ['plugins.AwesomePlugin'],
+        'plugins.AwesomePlugin': {
+            'some_credential': 'foo'
+        }
+    }
+
+    override = {
+        'AWESOME_PLUGIN_SOME_CREDENTIAL': 'bar'
+    }
+
+    with override_env(override):
+        load_overrides_from_env(config)
+        expected = {
+            'some_credential': 'bar'
+        }
+        assert config['plugins.AwesomePlugin'] == expected